The present invention relates to a carrying device employed in, for example, a semiconductor device fabricating system to carry semiconductor wafers, i.e., workpieces.
A conventional carrying device of this kind is used, for example, for carrying semiconductor wafers between a wafer storage chamber and a wafer processing chamber. Known carrying devices of this kind include those provided with a frog leg type arm and those provided with a parallel link type. A carrying device provided with a frog leg type arm has, for example, a pair of drive arms having base end parts connected to a drive shaft, a pair of front arms connected to front end parts of the drive arms by joints, respectively, and a wafer holder connected to front end parts of the front arms. For example, the front end parts of the pair of front arms are connected to the wafer holder by two rotating drums, i.e., upper and lower rotating drums. Two steel belts, i.e., upper and lower steel belts, are crossed around the upper and the lower drum, respectively, to turn the pair of front arms exactly synchronously through the same angle in the opposite directions, respectively. A gear mechanism is used instead of a position maintaining mechanism including rotating drums and steel belts. This position maintaining mechanism maintains the frog leg type arm in a symmetrical shape while the frog leg type arm is bent and stretched. The position maintaining mechanism is used as a power transmitting mechanism for the joint of a parallel link type arm.
In most cases, a hot, corrosive atmosphere is created in, for example, a semiconductor wafer processing chamber. When the arm including belts, such as steel belts, is moved into such a semiconductor wafer processing chamber, the belts are exposed to the hot, corrosive atmosphere. Belts, such as steel belts, have limited heat resistance and corrosion resistance and the hot, corrosive atmosphere in the processing chamber shortens the life of the belts. A carrying device employing gears is not subject to such problems that may be encountered by steel belts. However, gears are apt to produce dust and particles, and backlash between the mating gears causes problem in carrying accuracy.
The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a carrying device not employing any transmission mechanism including belts and gears, excellent in heat resistance and corrosion resistance, and capable of accurately and surely carrying a workpiece, such as a semiconductor wafer, always in a stable position.
According to a first invention of the present application, a carrying device comprises a support member; first and second shafts supported on the support member; a frog leg type arm having a base end part connected to the first and the second shaft; and a holding member for holding a workpiece, connected to a front end part of the frog leg type arm; wherein the frog leg type arm comprises: a rotatable first drive arm having a base end part mounted on the first shaft, a rotatable second drive arm having a base end part mounted on the second shaft, a first front arm having a base end part pivotally connected to a front end part of the first drive arm by a first joint and a second front arm having a base end part pivotally connected to a front end part of the second drive arm by a second joint; the holding member is connected by third and fourth joints to front end parts of the first and the second front arm; the holding member is linked to the first and the second front arm by a posture maintaining linkage having two similar antiparallel linkages, and the posture maintaining linkage controls turning of the holding member relative to the first and the second front arm.
According to a second invention, in the carrying device according to the first invention, the first and the second shaft are coaxial, the third and the fourth joint are coaxial, the first and the second drive arm and the first and the second front arm have the same length, a parallel linkage is formed by connecting opposite end parts of a links disposed opposite to the first drive arms to the first front arm and the second drive arm, and the parallel linkage has an uncontrollable and unstable point at a position other than a position where the coaxial third and fourth joints overlap the coaxial first and the second shaft.
According to a third invention of the present application, a carrying device comprises: a support member; first and second shafts coaxially supported on the support member; a frog leg type arm having a base end part connected to the first and the second shaft; and a holding member for holding a workpiece, connected to a front end part of the frog leg type arm; wherein the frog leg type arm comprises: a rotatable first drive arm having a base end part mounted on the first shaft, a rotatable second drive arm having a base end part mounted on the second shaft, a front arm having a base end part pivotally connected by a first joint to a front end part of the first drive arm and two links extended in parallel to the first drive arm and having opposite end parts connected to the front arm and the second drive arm; the first and the second drive arm, the front arm and the two links have the same length, and the first and the second drive arm, the front arm and the two links form two parallel linkages; the two parallel linkages have different uncontrollable and unstable points, respectively, and the first and the second drive arm and the front arm form three sides of a rhombus; the holding member is pivotally connected to a front end part of the front arm by a second joint; and the front arm, a front end part of the second drive arm and the holding member are linked by a posture maintaining linkage having two similar antiparallel linkages, and the posture maintaining linkage controls the turning of the holding member relative to the front arm.
According to a fourth invention, in the carrying device in the second or the third invention, the holding member is provided with workpiece holding parts at its opposite ends, and a joint is disposed at a middle point between the holding parts.
According to a fifth invention of the present application, a carrying device comprises: a support member; a parallel linkage type arm having a base end part supported on the support member; and a holding member for holding a workpiece, connected to a front end part of the parallel linkage type arm; wherein the parallel linkage type arm comprises: a first link fixed to the support member, a rotatable drive arm having a base end part mounted on a drive shaft penetrating an end part of the first link, a driven arm having a base end part pivotally connected to the other end of the first link by a first joint, a second link pivotally connected to front end parts of the drive arm and the driven arm by second and third joints, respectively, and first and second front arms having base end parts pivotally connected to the second link; the holding member is connected pivotally to front end parts of the first and the second front arm by fourth and fifth joints; and the drive arm or the driven arm, the second link, and the first or the second front arm are linked by a posture maintaining linkage having two similar antiparallel linkages, and the posture maintaining linkage makes the holding member move along a straight line.
The carrying device according to the first or the fifth invention is provided with a frog leg type arm or a parallel linkage type arm not having a transmission mechanism including belts or gears, excellent in heat resistance and corrosion resistance, and capable of accurately and surely carrying a workpiece, such as a semiconductor wafer, always in a stable position.
According to the second or the fourth invention, the carrying device is provided with a frog leg type arm capable of carrying a workpiece optionally forward or backward relative to the support member in the first invention.
The carrying device according to the third invention is provided with the frog leg type arm capable of exercising the same functions and the same effect as those of the first invention and of carrying a workpiece through a narrow opening.